Modeling and mapping of coastal processes (e.g. tsunamis, hurricane storm-surge, and
sea-level rise) requires digital representations of Earth's solid surface, referred
to as digital elevation models (DEMs). Some modeling utilizes structured, square-cell
DEMs, while others utilize unstructured grids that have no regular cell size or pattern.
Usually, these different DEM types are developed independently, even though they are
built from the same source bathymetric and topographic datasets. The National Geophysical
Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration
(NOAA), has developed two bathymetric-topographic square-celled DEMs and one bathymetric-topographic
unstructured DEM of southern Louisiana. The DEMs were developed for the Hurricane
Forecast Improvement Project (HFIP), with the purpose of developing a new methodology
for unstructured grid production from structured square-celled grids. The 1/3 arc-second
DEM referenced to North American Vertical Datum of 1988 (NAVD 88) was carefully developed
and evaluated. A NAVD 88 to mean high water (MHW) 1/3 arc-second conversion grid derived
from VDatum project areas was created to model the relationship between NAVD 88 and
MHW in the southern Louisiana region. NGDC combined the NAVD 88 DEM and the conversion
grid to develop a 1/3 arc-second MHW DEM. The NAVD 88 DEM was generated from diverse
digital datasets in the region. The DEMs were developed to be used for storm surge
inundation and sea level rise modeling. The source bathymetric and topographic datasets
used in the development of the NAVD 88 DEM were utilized along with the NAVD 88 DEM
and derivative grids to develop the NAVD 88 unstructured DEM.